linux-kernel - Re: [PATCH] perf inject: Fix --buildid-all not to eat up MMAP2

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Date:   Thu, 23 Feb 2023 10:31:57 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-perf-users@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] perf inject: Fix --buildid-all not to eat up MMAP2

Em Wed, Feb 22, 2023 at 11:01:55PM -0800, Namhyung Kim escreveu:
> When MMAP2 has PERF_RECORD_MISC_MMAP_BUILD_ID flag, it means the record
> already has the build-id info.  So it marks the DSO as hit, to skip if
> the same DSO is not processed if it happens to miss the build-id later.
> 
> But it missed to copy the MMAP2 record itself so it'd fail to symbolize
> samples for those regions.

Thanks, applied.

- Arnaldo

 
> For example, the following generates 249 MMAP2 events.
> 
>   $ perf record --buildid-mmap -o- true | perf report --stat -i- | grep MMAP2
>            MMAP2 events:        249  (86.8%)
> 
> Adding perf inject should not change the number of events like this
> 
>   $ perf record --buildid-mmap -o- true | perf inject -b | \
>   > perf report --stat -i- | grep MMAP2
>            MMAP2 events:        249  (86.5%)
> 
> But when --buildid-all is used, it eats most of the MMAP2 events.
> 
>   $ perf record --buildid-mmap -o- true | perf inject -b --buildid-all | \
>   > perf report --stat -i- | grep MMAP2
>            MMAP2 events:          1  ( 2.5%)
> 
> With this patch, it shows the original number now.
> 
>   $ perf record --buildid-mmap -o- true | perf inject -b --buildid-all | \
>   > perf report --stat -i- | grep MMAP2
>            MMAP2 events:        249  (86.5%)
> 
> Cc: stable@...r.kernel.org
> Fixes: f7fc0d1c915a ("perf inject: Do not inject BUILD_ID record if MMAP2 has it")
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> ---
>  tools/perf/builtin-inject.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c
> index f8182417b734..10bb1d494258 100644
> --- a/tools/perf/builtin-inject.c
> +++ b/tools/perf/builtin-inject.c
> @@ -538,6 +538,7 @@ static int perf_event__repipe_buildid_mmap2(struct perf_tool *tool,
>  			dso->hit = 1;
>  		}
>  		dso__put(dso);
> +		perf_event__repipe(tool, event, sample, machine);
>  		return 0;
>  	}
>  
> -- 
> 2.39.2.637.g21b0678d19-goog
> 

-- 

- Arnaldo